Radiation-pyrometer.



. temperature of the body serian sTATnS A;

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antenna: sTEWnT WHIPPLEOF CAMBRIDGE, ENGLAND, Asslelvon 'To THE TAYLORrNsTnUvi/LENT COMPANIES, or ROCHESTER, NEW Your;l

RADIATION-PYROMETER'.

- Applcationled August 18, 1910. Serial No. 577,795.-

To LEZ Iwilma t may concern:

Be it known that I, ROBERT STEWART lflnirrnn, a subjectof the King ofEngland, residing at Cambridge, county of Cambridge, England, haveinvented certain new and usefui Improvements in Radiatioiv Pyremeters,of lwhich the following is a specification.

This invention relates to radiation pyronieters, that is, to pyrometersin which the whose temperature is required but to a portion oftheradiant heat therefrom, so that the sensitiveelement is only raised -intemperature by a. fraction of the true temperature ofthe body.r

The great advantage of radiation py'-4 rometers is that owing to thefact just mentioned the sensitive element does notvvear outrapidly eventhough it is used to meas` ure extremely high'temperatures. The chiefdisadvantage in radiation-pyrometers hitherto` used `is that theirreadings depend s not only upon the temperature of the body yitself butupon the nature of the surface of ythe body and on the'temperature ofsurrounding objects.

` these pyiometers For instance, if one of be used to determine thetemperature of the molten metal ina crucible, the-reading obtained byasighting on the surface of the metal will be considerably lower whenthe Crucible is in the open air than it Will be when the Crucible isinside a closed furnace. the Walls of which are at approximately. thesame temperature as' the metal. This isl due to the fact that in thelatter case the Crucible of metal is vsurrounded by a black body, Whilevin the former case this vis not so; and molten metal not being itself ablack body the readings obtained are therefore low. lt is therefore inmany cases necessary to apply corrections to the readings obtained byradiation pyrometers in order to obtain true temperatures. Also mosttypes of radiation pyrometers have the `further disadvantage that theyrequire focusing on the specificati@ of Letters Patent.

Patented Jan. 19, 1915.

the necessity of focusing the instrumentl bei fore a reading is taken.

In aradiation pyrometer according to this invention aciosed conduitwhich is also closed at one end is so arranged that he'at radiated alongthe conduit from its closed end is always focused lon to the sensitiveelement Without preliminary adjustment. i

More particularly. this pyrometer comprises the combination of a tubeclosed.v at sensitive element 1s not sub3ected to the actual one end butopenat the other end, a` heat sensitive element situated in the open endof the tube and a device for concentrating heat radiated from the insideof the closed endf of the-tube on to the sensitive surface.

' According tov one modification ofthe inseveral constructions by whichit may be carried into effect.

Figure 1 is a longitudinalsectional view of one end of a pyrometer,constructed in accordance with a preferred embodimentv of the invention;Fig. 1 is a similar vieuT of the opposite end; Fig. 2 is a similar'viewof another modified form, and Fig. 3 is a similar View` of a furthermodiication.

As illustrated in Figs. 1 and la a tube A A1 is employed of definitelength and closed at the end A2, having mounted at the other end apyrometer head A3 of special design containing the sensitive element B.A con`v cave mirror C of short focal length is-mounted in this pyrometerheadfin such 'a manner that an image ofthe inside of the closed end ofthe tube is formedI a few: inchesin front of the mirror. The sensitiveelement B is so situated that this image .coincides with it. To use thepyrometer the closed end A2 of thevtube is inserted in the furnace,Crucible of molten metal7 or other body Whose temperature is required,the other i end of the tube carrying the pyrometer head 1 A3 remainingat a comparatively lfz-"i' tem-1.. perature. The sensitive element eforehas its temperature raised above' the temthe closed end ofthe tube.

perature of the surrounding pyrometer head by an amount dependent uponthe intensity of the heat image formed by the mirror and therefore by anamount dependent upon the temperature of the closed end of the pyrometertube. Since for the same pyrometer the concave mirror is always at thesame distance from the closed end `oi thetube; the instrument can beadjusted so that the image coincides with the sensitive element once forall, and will therefore not need focusing or otherwise adjusting eachtime itis used.

Also, since the pyrometer tube will in practice be made of a fairlysmall diameter and will' be subjected to the heat of the furnace `for`alen'gth of several diameters measured froml the closedend, theconditionsneces-f sary for true blackl body radiation from ,the

inside oit the'closed end of the tube are se# cured and the readingswill therefore' be in'- `surface 'of dependent of the nature of the A`variety of differenty devices may be made useof for the sensitiveelement, one of the simplest being to use a small thermo couple' asdiagrammatically illustrated in Fig. 1, this being connected by leads Dfrom thepyrometer head toan indicating'cr refV cordinginillivoltmeter Eor suitable current' lmeasuringfdevice lWhose scale is calibrated interms of the temperature of vthe .closed end of the tube. Other devicesmight be used depending for their principle of' oper`v` ationonL thechange of resistance of a Wire withy temperature; or the expansion ofmetals with temperature etc` `Itivfill be seen that the onl part of ,thepyrometer which is subjcte to the full, temperature being measured isthat portion of the tubevAu near and at the closed end A2. Provision istherefore made for renewing this portion quickly and cheaply by makingtheltube in two parts'. Therenewable end portion A need not necessarilybev of the samergzmaterial or size as'the other permanentpition andwhile the latterl will usually be" of steel, the renewable portion maybeof steel, porcelain, silica, plumbago etc.,y according to thetemperature and purposefor which the instrument isvused.v

It is obvious that modifications may be made in` carrying this inventioninto el'ect for example although a concave mirror has.

been mentioned as the means of producing the heat. image which coincideswith the sensitive element, other methods ofvproducing this irnzngevmight be used.A

l'n certain cases, as'for instance when used for measuring'thetemperature of crucibles of molten metal itmay be an advantage to havethe pyrometer of an L shape as illustrated in Figs. 2 and 3. This mayeasily be 'obtainediby fixing a vmirror in the angle so that the heatrays received on it from the closed end of the tube are deflected alonthe axis of thel ytube to the pyrometer hea f In the constructionillustrated in Fi 2 4construction provided always that the spirit oftheinvention is not departed from.

What claim as m to secureby Letters atent is la A radiationy pyrometercomprising a. portable tube having one end closed, said' end bcingformedof opaque material andv adapted to be subjected to the source of heat, asensitive element disposed in `'proximity to the opposite end of thetube, and means for'concentrating thel heat upon said sensitive element.

2. Avradiation yrometer comprlslng a. hollow portable I evicev havingone end p forming a black body adapted tobe subjected tothe source ofheat, a sensitive element disposed in proximity to the opposite end-ofthe tube, and means for concentratthe heat uponthe sensitive elementi@in Itestfunony whereof I have signed my name tothis specilication in thepresence of two subscribing witnesses.

Witnesses: v

HARRY Gr. Gruen, P. H RU'NDELL ROBERT STEWART WHIPLPLE. f

invention and desire f

